Green reverse water gas shift reaction achieved by microwave-induced plasma

The reverse water-gas shift (RWGS) reaction is a promising route to produce syngas that is a valuable precursor for synthetic fuel production. However, this reaction is possible only using catalysts. In this study the catalyst is replaced by microwave-induced plasma. The experimental setup employs a microwave plasma reactor operating at atmospheric pressure, utilizing carbon dioxide and hydrogen as reactants, with the output gas analyzed by gas chromatography. The maximum concentration of about 41 vol% of CO can be obtained from the equimolar mixture of CO2 and H2 inlet gases after water vapor is condensed out of it. This is much higher compared to the about 2% yield of CO obtained by the same microwave procedure using pure CO2 plasma. A thermodynamic model is shown to reproduce the experimental results if the temperature of the gas is in the range of 1,000-1,500 K and decreasing with increasing flow rate. A control experiment was run without the presence of microwave excited plasma or catalyst with no CO formed as a result. Thus, the 41 vol% of CO formation is mostly due to the microwave excited plasma, presenting a viable alternative to catalysts for sustainable syngas production.